Focused treatment tip design and method to optimize heat transfer through low temperature fluids and gases

ABSTRACT

A focused treatment tip (FTT) for controlling the evaporation rate and providing targeted delivery of low temperature liquified gases for contact with living tissue includes a contoured body. When filled with liquified gas, the device insulates the gas from waste heat sources, such as the surrounding environment. The device can control the evaporation rate of the liquified gas at the treatment site. The controlled evaporation rate affects the rate of heat transfer from the treated tissue allowing for controlled exposure times and desired outcomes. The device can be used with various application tips to further define the target tissue area to be treated while minimizing collateral damage to surrounding tissue and isolating the gas within the contoured body and focusing heat transfer to the desired treatment area. The device may use transparent materials that make the treatment visible to the operator while the liquified gas is evaporating.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/857,642 filed on Apr. 24, 2020, and claims the benefit of priority ofU.S. Provisional Application No. 62/839,156 filed on Apr. 26, 2019. Thisapplication incorporates by reference the entire contents of both U.S.patent application Ser. No. 16/857,642 filed on Apr. 24, 2020, and U.S.Provisional Application No. 62/839,156 filed on Apr. 26, 2019.

TECHNICAL FIELD

The invention relates to cryosurgical devices and methods of treatingtissues to remove unwanted topical lesions. In particular, the inventionrelates to devices and methods to isolate applied liquified gases,focusing their potential heat transfer on the target tissue, andcontrolling heat lost to secondary sources, such as the surroundingenvironment. The geometric construction of the devices provides freezingand controls the rate of evaporation and, therefore, the rate of heattransfer at the interface between the gas and target tissue.

BACKGROUND

The treatment of cutaneous lesions on humans and animals is oftenaccomplished by dispensing liquified gases into a cone or funnel. Incutaneous cryosurgeries, the liquified gas contacts the treatmentsurface, draws heat from the contact point with the tissue, and freezesthe tissue by overcoming the local tissue temperature when the liquifiedgas is allowed to stay in contact long enough or when sufficientliquified gas is applied. The cells in the frozen tissue are damaged andare eventually sloughed off by the body resulting in new cell growth.

Existing cryosurgical devices and methods use a simple cone or funneldesign to direct the liquified gas to the target spot (treatment area).This results in rapid evaporation due to the liquified gas drawing heatnot only from the target contact spot, but also from the surroundingenvironment and cone materials. This results in an inconsistenttreatment and an overall decrease in efficacy as reflected by the needfor more gas to achieve the desired result. Existing cone or funneldesigns have a large open end, maximizing the area for heat loss to theenvironment instead of concentrating it towards the treatment area. Theinefficiency of current designs results in increased treatment times andincreased volumes of liquified gas applied to the target spot beingtreated.

SUMMARY

The methods and devices of the invention include focused treatment tips(FTT) and overcome the inefficiency of previous designs by controllingheat transfer from the surrounding environment. The materials selectedfor the FTTs provide enhanced focus on the target spot being treated andprovide further improvements and benefits over prior systems. Theinvention includes improved constructions of the interface at thesurface of the skin and the head space above the gas. The inventionprovides an improved gas dispenser interface. The invention providesimproved methods of controlling the rate of evaporation and enhancesheat transfer at the surface of the skin and target treatment spot. Theinvention provides a more effective cryosurgical treatment of lesionswhile using less liquified gas to achieve the result.

The invention can be used with other apparatus and/or methods thatdispense liquified gases. The invention includes a focused treatment tip(FTT) that provides a targeted heat transfer from treatment surfaces andfrom target tissues when placed into contact and supplied with liquifiedgas. The FTT can be fit with interchangeable application tips that allowtreatment of lesions of varying shapes and sizes. The FTT can be clearor opaque and can be composed of polymers, elastomers, metals, silica,and combinations of these materials. In one example embodiment of theinvention, translucent materials are used to allow the observation ofthe liquified gas “boiling,” while dwelling at the FTT interface withthe treatment spot. The improved visual observation allows an operatorto monitor the treatment over time.

The invention allows the operator to control the time that the liquifiedgas is in contact with the target skin through evaporation and theamount of heat transferred during the gas contact period. To controlthis timing and delivery, FTTs in accordance with the invention includefeatures that influence the rate of evaporation and provide controlagainst random heat acting as the primarily cause of evaporation of theliquified gas. FTTs in accordance with the invention are designed andmanufactured to provide these controls based on geometric and materialselections of the sections of the FTTs where they contact the treatmentarea (i.e., interface at the skin), in the boiling section, and in theevaporation control section.

The interface section of the FTTs at the skin cover the target treatmentarea while minimizing the volume of liquified gas needed to cover thetarget skin. To provide these features, the interface tip section isshaped to match the geometry of the skin being treated.

In some example embodiments of the invention, the FTT includes anapplication treatment tip with various geometries (e.g., diameters) anddepths to allow targeted treatments to match lesion sizes. Theapplication tips can be made of various materials and may be reusedafter appropriate sterilization or discarded. The application tips canbe of various shapes for the surface interface and skin contact, (e.g.,ovals, squares, rounded squares, diamonds, rounded diamonds, triangles,rounded triangles, and other geometrical shapes with or without roundedcorners and/or edges). The method of making the seal between the FTT andthe skin may be through mechanical pressure, adhesives, or multilayeredlaminates.

The boiling section is in fluid communication with the skin interfacesection and is adjacent to the skin interface section and is designedand manufactured to allow the liquified gas to evaporate within aconfined space, thus limiting the exposed surface area of the liquifiedgas to the environment surrounding the device. The portion of theboiling area opposite the skin interface section is in fluidcommunication and adjacent to the evaporation control section. Theboiling section dimensions can be adjusted on each end (the end adjacentto the skin interface section and the end adjacent to the evaporationcontrol section) to speed or slow the evaporation rate of the liquifiedgas.

The evaporation control section is the main interface between the openenvironment and the gas. Vapor transfer takes place in this section, andthe amount of surface area and the unobstructed opening size of theevaporation control section serves to control the rates of evaporation.The sizes and geometries of the evaporation control section can bemodified to control the rates of evaporation. In tandem with theinterface section of the FTT, as the size of the interface sectionincreases, so does the heat loss, which increases the rate ofevaporation.

The combination of the skin interface section, the boiling section, andthe evaporation section combine in the FTTs in accordance with theinvention to control the rate of evaporation for cryogen gases used forcryosurgical treatments.

In one example embodiment of the invention, a focused treatment tip(FTT) device interfaces with a cryosurgical device and providesevaporation rate control of liquified gases in contact with a patient.The focused treatment tips (FTTs) include an evaporation control sectionthat receives the cryosurgical device, a boiling section that is influid communication with the evaporation control section also in fluidcommunication with an application tip section. That is, the boilingsection is between the evaporation control section and the applicationtip section. The boiling sections include a determined space for vaportransfer of the liquified gas when treating a targeted tissue treatmentsite of the patient. The application tips (“skin interface”) cover thetargeted tissue treatment site of the patient and seal the FTT device tothe tissue treatment site of the patient.

In one example embodiment of the invention, an FTT device includes aclear or opaque material, enabling a user or operator to observe boilingof the liquified gas during the treatments. The materials can includepolymers, elastomers, metals, silica, and combinations of thesematerials.

In example embodiments of the invention, the FTT devices include acontoured elongated body for one-handed operation. Prior commercialproducts with cones required a two-handed operation with one handholding the cone in contact with the skin at the target lesion whilesimultaneously using a second hand to dispense gas into the cone,allowing it to evaporate. Prior systems suffered from rapid evaporationcaused by heat from waste sources, such as the local environment andsurroundings and must be filled several times to treat the target areafor a sufficient amount of time for the desired treatment effect.

As well, the volume of the boiling section is proportional to theevaporation rate of the liquified gas. The geometric dimensions of theboiling section can be selected and manufactured to provide a targetevaporation rate or range of evaporation rates of the liquified gas.

The liquified gases used in accordance with the invention includehydrocarbons, fluorocarbons, hydrofluoro-olefins, and hydrofluorocarbonblends. Likewise, the liquefied gases used include propane, butane,dimethylether, 1,1,1,-trifluoroethane, pentafluoroethane,difluoromethanene, trifluoromethane, chlorodifluoromethane,1,3,3,3-Tetrafluoropropene, and nitrous oxide.

The application tip section of the FTTs in accordance with the inventionare sized and shaped to approximate the size and shape of the targetedtissue treatment site. For example, the application tip section of theFTTs can be ovals, squares, rounded squares, diamonds, rounded diamonds,triangles, rounded triangles, and other geometric shapes.

One example embodiment of the invention includes a cryosurgical device,including a liquified gas delivery device and a focused treatment tip(FTT) device as outlined above. Another example embodiment of theinvention includes a method for treating a skin lesion using acryosurgical device with a focused treatment tip (FTT) device. Onemethod includes positioning the FTT device against a targeted tissuetreatment site or over a skin area to be treated. The example method inaccordance with the invention includes receiving liquified gas into theFTT device to a determined fill level and maintaining the FTT deviceagainst the targeted tissue treatment site while the liquified gas isevaporating. As the liquified gas evaporates, the liquified gas drawsheat from the skin/tissue treatment site. Once the liquified gasevaporates, the FTT is removed from the treatment area. In one exampleembodiment, the method of treating the skin lesion can be repeated whenan additional application is indicated. The cells at the treated spotare now damaged or destroyed, and the body will slough off the damagedcells in approximately two weeks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a cryosurgical device including anFTT (focused treatment tip) device for cryosurgical applications inaccordance with the invention.

FIG. 2 shows a perspective view of an FTT device for cryosurgicalapplications in accordance with the invention.

FIG. 3 shows a side view of an FTT device for cryosurgical applicationsin accordance with the invention.

FIG. 4 shows a top view of an FTT device for cryosurgical applicationsin accordance with the invention.

FIG. 5 is a graph of temperature variance over time of a liquified gasduring a cryosurgical treatment in accordance with the invention.

FIG. 6A shows a side view of an application tip skin interface inaccordance with embodiments of the invention.

FIG. 6B shows a perspective view of an application tip skin interface inaccordance with multiple embodiments of the invention.

FIG. 7 describes a method of using an FTT device for cryosurgicalapplications in accordance with the invention.

DETAILED DESCRIPTION

The FTT (focused treatment tip) devices of the invention delivercryosurgical substances to affected patient areas for treatments.

System Components

As shown in FIG. 1, a cryosurgical system 100 includes an FTT device 101configured to mate with a cryosurgical device 103 for cryosurgicaltreatments. The cryosurgical substance delivery device 103 can be anynumber of liquified gas delivery devices for targeting affected skin.The cryosurgical device 103 may include a storage container forliquified gas and a dispersal mechanism to dispense the stored liquifiedgas for cryosurgical treatment. The cryosurgical device 103 may alsodispense various cryogens for use with the FTT device 101.

The FTT devices 101 may include many shapes and sizes to be adapted totreatment sizes and shapes of treatment locations. The FTT devices 101may include a contoured elongated body to provide space for evaporationof the liquified gas for an effective time of delivery. The FTT devices101 of the invention can include clear or opaque material compositionsto allow for user observation of the cryosurgical substances as itboils/bubbles and evaporates once the cryosurgical substance isdispensed. Additionally, the FTT devices 101 are configured to mate withthe cryosurgical device 103 to provide single-handed control of thecryosurgical system during treatment. The FTT devices 101 limit theeffects of environmental evaporation and seal the delivery of theliquified gas to the affected skin to provide more effectivecryosurgical treatment.

As shown in FIGS. 2-4, the FTT devices 101 include at least threedesigned sections: (1) an evaporation control section 201; (2) a boilingsection 203; and (3) an application tip skin interface 205. The FTTdevices 101 may be unibody devices, or multi-bodied interfacing deviceswhich have interchangeable evaporation control sections 201, boilingsections 203, and application tip to skin interfaces 205 to configure tothe geometry of the affected skin, the mating portion of thecryosurgical device 103, and for providing space for vaporization of thecryogen gas. The sections 201-205 of the FTT devices 101 control therate of evaporation by defining the geometry of each section of the FTT.The sections may be optimally configured and manufactured based on thetype of liquified gas used for treatments and the boiling temperaturesof those liquified gases being used. Similarly, the sections can beconfigured based on the size and shape of the affected skin oranatomical region undergoing treatment.

The evaporation control section 201 initially receive a liquified gasfrom a cryosurgical device 103. The evaporation control section 201 isthe main interface between the open and uncontrolled environment and theliquified gas, and thus greatly controls evaporation of the liquifiedgas. Vaporization takes place within the cross-sectional area of theevaporation control section 201 interfacing to the cryosurgical device103. For example, the cross-sectional area of the evaporation controlsection 201 and the volume of space within the evaporation controlsection 201 (i.e., the cross-sectional area in combination with thelength) controls the rates of evaporation.

The boiling section 203 is between the evaporation control section 201and the application tip skin interface 205. The boiling section 203 isconfigured and manufactured to allow the gas to evaporate within aconfined volume, thus limiting the environmental thermal effects on theliquified gas to control vaporization prior to treatment. The boilingsection 203 dimensions may be adjusted on each end (i.e., at the endthat interfaces with the evaporation control section 201 and at the endthat interfaces with the application tip skin interface 205) in order tospeed or slow evaporation. For example, the boiling section 203 may beincreased in length, width, or cross-sectional area to increase thesurface area of the liquified gas to allow proportionally fasterevaporation of the liquified gas.

The configurations of the cross-sectional areas of the evaporationcontrol section 201 and boiling section 203 may be shaped in variousways, but as the size of the interface with the cryosurgical device 103increases with the environment, so will the heat losses, thus increasingthe gas evaporation. Thus, the evaporation control section 201 andboiling section 203 are configured and manufactured to more effectivelymaintain the temperature of the liquified gas by controlling the surfacearea of the connection to the cryosurgical device 103 therebycontrolling the rate of evaporation of the liquified gas. Theevaporation control section 201 and boiling section 203 may beconfigured and manufactured to mate with various cryosurgical devices103 to provide single-handed use of the cryosurgical system 100. Thus,the dimensions of such a mating interface with the evaporation controlsection 201 and boiling section 203 may determine the length of theevaporation control section 201 and boiling section 203. For example, awider interface opening may result in a shorter evaporation controlsection 201 and/or boiling section 203.

The application tip skin interface 205 is configured and manufactured toapproximately cover only the target skin to be treated to both minimizethe volume of liquified gas that is used on the patient's target skin,and also to minimize the cryosurgical effects on the patient's healthyskin (i.e., collateral tissue damage). Thus, the interface tip may beshaped to match the target skin. Different configurations for theinterfaces are further shown in FIGS. 6A and 6B. In embodiments wherethe application tip skin interfaces 205 are separate from theevaporation control section 201 and the boiling section 203, theinterfaces 205 are configured to mate with the boiling section 203 toenable single-handed use allowing for greater flexibility to the user.

As shown in FIGS. 6A and 6B, in some embodiments of the invention,application tip skin interface 205 may be circular or ovular in shape,however, in other embodiments of the invention the skin interfaces 205may include any number of geometric shapes including ovals, squares,rounded squares, rhombuses, diamonds, rounded diamonds, triangles,rounded triangles, and other geometrical shapes with or without roundedcorners and/or edges. The skin interfaces 205 may also be adjusted tovarious non-normal geometric shapes (e.g., irregular shapes), forexample, if the FTT device 101 is made from a malleable and/or moldableor cuttable material. As shown in embodiments 205 a-205 j in FIGS. 6Aand 6B, the skin interfaces 205 may vary in size/shape. The skininterfaces 205 may vary in size, at least from 3-12 mm diameter (asshown in Table 1 below), however, may be configured to surround as muchof the patient skin to be treated as possible.

A method of using the FTT device 101 with a cryosurgical system 100 isshown in blocks 701-707 of FIG. 7. As described in block 701, the FTTdevice 101, while mated to a dispensing device 103, is placed over andagainst the skin area to be treated with a liquified gas. The size andshape of the selected FTT device 101 is determined by approximating thesize and shape of the area of the skin to be treated. This approximationlimits damage to healthy skin.

In block 703, the dispensing device 103 dispenses the liquified gas intothe FTT device 101 to a desired fill level. Because the FTT device 101is made of transparent or opaque materials, the user of the cryosurgicaldevice 100 may be able to see the liquified gas in the FTT device 101.In block 705, the liquified gas is allowed to boil or bubble to drawheat from the treated skin. In block 707, the user watches theboiling/bubbling until it ends, i.e., the liquified gas has evaporated.The user may then remove the FTT device from the skin to determinewhether the treatment was completed or if the treatment should berepeated. If repeated, the user may perform blocks 701-707 again totreat the affected skin.

FTT Vs. Conventional Cone Comparison

In one experiment, approximately the same weight (0.7-0.8 g) of a gasmixture of pentafluoroethane (50%), difluoromethane (50%) was dispensedinto the new invention FTT design and into a conventional product,Verruca-Freeze™, which uses a cone design originally disclosed in U.S.Pat. No. 5,200,170. Both the prior cone and the FTT device have acircular application area which is 5 mm in diameter. A thermocoupleinserted beneath the orifice of the prior art cone and of the FTT wasused to measure the temperature and time profile inside the bottom ofeach device to determine evaporation rates of the liquified gas in eachdevice. As shown in FIG. 5, the FTT of the invention was able to holdits temperature substantially longer below −48° C., which is themeasurable boiling point of the mixture of pentafluoroethane (50%),difluoromethane (50%) that was dispensed. The cone remained below −48°C. for 13±4 seconds, while the FTT of the invention remained below −48°C. for 25±6.7 seconds. Thus, the FTT device, in this example, was 100%more effective at controlling the rate of evaporation, which thereforeincreased the potential heat transferred from the target area.

In other experiments, the FTT devices and the Verruca-Freeze™ cones werefilled again with approximately 1.3 g of the same liquified gas mix, andthe time and temperature were measured until the liquified gas fullyevaporated. The size of the interface to the skin was varied (i.e., thecross-sectional area of the skin interface 205 changed), and the surfaceto which the gas was applied (target treatment area) was varied.

As shown also in Table 1 below, the FTT device 101 more effectivelyslows the vaporization of the liquified gas. This effect was enhanced asthe surface area of the treatment interface was increased while the massof gas applied remained fixed. This increase in surface area at theinterface corresponds with an increased influence from waste heat in thesurrounding environment causing the gas in the cone to more quicklyevaporate than gas in the FTT device 101. Thus, the FTT device lessensthe amount of gas needed to increase potential heat transfer timesresulting in an improved efficiency of the system.

TABLE 1 Application Tip Skin FTT Average Conventional Cone InterfaceDiameter Time Below Average Time Below % (mm) −48° C. (s) −48° C. (s)Difference 3 99.6 76.6 23 5 72.8 58.2 21 9 49.6 41 18 12 32.4 17.6 44

The invention addresses design and ease of use difficulties of manypreviously available cryosurgical substance application systems. Theinvention provides an economical and easy to use platform whenperforming a large number of cryosurgical treatments.

The claimed invention is:
 1. A focused treatment tip (FTT) device tointerface with a cryosurgical device for evaporation rate control ofliquified gas in contact with a patient, comprising: an evaporationcontrol section that receives the cryosurgical device; a boiling sectionin fluid communication with and between the evaporation control sectionand an application tip, the boiling section including a determined spacefor evaporation of the liquified gas while treating a targeted tissuetreatment site of the patient; and an application tip skin interface tocover the targeted tissue treatment site of the patient and seal the FTTdevice to the tissue treatment site of the patient.
 2. The FTT device ofclaim 1, wherein the FTT device includes a clear or opaque material toobserve boiling of the liquified gas.
 3. The FTT device of claim 1,wherein the FTT device includes at least one selected from the group ofa polymer, elastomer, metal, and silica.
 4. The FTT device of claim 1,wherein the FTT device includes a contoured elongated body.
 5. The FTTdevice of claim 1, wherein the volume of the boiling section isproportional to the evaporation rate of the liquified gas.
 6. The FTTdevice of claim 1, wherein the surface area of the evaporation sectionis proportional to the evaporation rate of the liquified gas.
 7. The FTTdevice of claim 1, wherein the liquified gas includes at least onematerial selected from the group of a hydrocarbon, fluorocarbon,hydrofluoro-olefin, and hydrofluorocarbon blend.
 8. The FTT device ofclaim 7, wherein the at least one material includes at least onematerial selected from the group of propane, butane, dimethylether,1,1,1,-trifluoroethane, pentafluoroethane, difluoromethanene,trifluoromethane, chlorodifluoromethane, 1,3,3,3-tetrafluoropropene, andnitrous oxide.
 9. The FTT device of claim 1, wherein the application tipis sized and shaped to approximate the size and shape of the targetedtissue treatment site in an oval, square, rounded square, diamond,rounded diamond, triangle, rounded triangle or other geometric shape.10. A cryosurgical system, comprising: a liquified gas delivery device;and a focused treatment tip (FTT) device, comprising: an evaporationcontrol section that receives the liquified gas; a boiling section influid communication with and between the evaporation control section andan application tip, the boiling section including a determined space forevaporation of the liquified gas while treating a targeted tissuetreatment site of a patient; and an application tip to cover thetargeted tissue treatment site and seal the FTT device to the tissuetreatment site of the patient.
 11. The cryosurgical system of claim 10,wherein the FTT includes a clear or opaque material to observe boilingof the liquified gas.
 12. The cryosurgical system of claim 10, whereinthe FTT device includes at least one selected from the group of apolymer, elastomer, metal, or silica.
 13. The cryosurgical system ofclaim 9, wherein the FTT device includes a contoured elongated body. 14.The cryosurgical system of claim 10, wherein the volume of the boilingsection is proportional to the evaporation rate of the liquified gas.15. The cryosurgical system of claim 1, wherein the surface area of theevaporation section is proportional to the evaporation rate of theliquified gas.
 16. The cryosurgical system of claim 10, wherein theliquified gas includes at least one material selected from the group ofa hydrocarbon, fluorocarbon, hydrofluoro-olefin, and hydrofluorocarbonblend.
 17. The cryosurgical system of claim 16, wherein the at least onematerial includes at least one material selected from the group ofpropane, butane, dimethylether, 1,1,1,-trifluoroethane,pentafluoroethane, difluoromethanene, trifluoromethane,chlorodifluoromethane, 1,3,3,3-tetrafluoropropene, and nitrous oxide.18. The cryosurgical system of claim 10, wherein the application tip issized and shaped to approximate the size and shape of the targetedtissue treatment site in an oval, square, rounded square, diamond,rounded diamond, triangle, rounded triangle or other geometric shape.19. A method for treating a skin lesion as described above using acryosurgical device with a focused treatment tip (FTT) device,comprising: positioning the FTT device against a targeted tissuetreatment site; receiving liquified gas into the FTT device; andmaintaining the FTT device against the targeted tissue treatment sitewhile the liquified gas is evaporating.
 20. The method of claim 17,further comprising: dispensing the liquified gas against the targetedtissue treatment site when an additional application is indicated.